Should exercises and training be specific in motor learning?

Lisa Harvey and colleagues have made a major contribution to the rehabilitation of spinal cord injuries so it is a pleasure to have a chance to engage with them in a discussion of some aspects of their paper (Harvey et al 2011). The aim of this study was to investigate whether people with recently acquired paraplegia benefit from an intensive motor training program aimed at improving unsupported sitting. All subjects undertook standard inpatient rehabilitation that included physiotherapy and occupational therapy training for transfers, wheelchair skills, dressing, and showering. Experimental subjects received three additional 30 min sessions per week for 6 weeks, of exercises directed at improving the ability to sit unsupported. At the end of the study both experimental and control participants had improved. However, there were no significant differences between the groups rendering, in the authors' opinion, the additional training redundant. The results of this study raise some interesting questions about the specificity of exercises and training in motor learning and in the acquisition of skill; in particular, can one expect exercises aimed at improving specific movements (eg, Fig 1, Harvey et al 2011) to generalise into improved performance of complex functional tasks such as dressing, showering, brushing teeth, and wheelchair skills? The history of specificity studies tells us this may not occur unless the action being trained has similar biomechanical characteristics to the activity to be learned. This issue is of some importance for physiotherapists in many fields of neurorehabilitation. People with paraplegia perform most of their activities of daily life in a wheelchair. Learning to balance in sitting is therefore fundamental to vocational, recreational, sporting, and social participation, and to quality of life. For physiotherapists and occupational therapists to train complex functional tasks in sitting, they must be able to analyse the nature of the task to derive effective therapeutic interventions (Gentile 2000): in this instance, in planning an exercise program, it is necessary to have some understanding of the biomechanics of sitting balance in able-bodied subjects and the critical features of balance, as well as the effects of muscle weakness and paralysis on actions performed in sitting. Biomechanical studies of able-bodied subjects have shown us that leg muscles play an active role in supporting and balancing the body mass over the base of support (thighs and feet) when we move about in sitting. In studies of reaching forward beyond arms' length, leg muscles were active before …